This invention relates to silicone tubes having an internal layer of reinforcing braiding and, more particularly, to a method for forming a clampable fitting at the end of such a tube.
Since silicone is a relatively inert chemical in aqueous solutions, i.e., it does not react with contacting liquids or leach chemicals into contacting liquids, it is a material that has obvious advantages in use as tubing for many applications, including pharmaceutical manufacture and intravenous drug delivery. In some of these applications, a quick-disconnect clampable fitting is used for the interconnection of such silicone tubes. U.S. Pat. No. 5,320,389, discloses such a fitting which is designed to be secured to the end of a tube in the field. For high pressure applications, the silicone tubes have an intermediate internal layer of reinforcing braiding sandwiched between inner and outer layers of silicone. The braiding is usually made of polyester or a Kevlar-like material. In the past, problems have been encountered where the braiding is pulled, within the tube, away from the fitting, causing a failure of the tube. It would therefore be desirable to have a method of providing a fitting at the end of a reinforced silicone tube which does not suffer from the aforedescribed disadvantages.
According to the present invention, a method for forming a fitting at an end of a silicone tube having an internal layer of reinforcing braiding comprises the steps of removing the outer silicone layer of the tube for a predetermined length from the end of the tube to expose the internal layer of the braiding along that length, placing a first silicone ring over the exposed layer of braiding, folding the exposed layer of braiding over the first ring, and placing a second silicone ring over the folded-over layer of braiding. A mold having a cavity shaped as a desired fitting is provided and the tube end with the first and second rings is inserted into the mold cavity. The mold cavity is then filled with liquid silicone, which is heated and cured to form a fitting and the fitting is then removed from the mold cavity.
In accordance with an aspect of this invention, the first ring is placed substantially midway along the fixed length of exposed braiding. Accordingly, when the exposed braiding is folded over the first ring, there is no overlap of the exposed braiding over the uncut outer silicone layer of the tube.